Topic: Types of elemental carbon

Target group

High school / technical school student

Core curriculum:

New core curriculum:

High school and technical high school – basic level:

III. Chemical bonds. Intermolecular interactions. Pupil:

7) explains the concept of elemental allotropy; based on knowledge of the construction of diamond, graphite, graphene and fullerenes, explains their properties and applications.

High school and technical high school – extended level:

III. Chemical bonds. Intermolecular interactions. Pupil:

9) explains the concept of elemental allotropy; based on knowledge of the construction of diamond, graphite, graphene and fullerenes, explains their properties and applications.

Old core curriculum:

High school and technical high school – basic level:

III. Chemical bonds. Intermolecular interactions. Pupil:

7) explains the concept of elemental allotropy; based on knowledge of the construction of diamond, graphite, graphene and fullerenes, explains their properties and applications.

General aim of education

The student justifies the dependence of properties and applications of diamond, graphite, fullerenes and graphene on their internal structure

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to describe the location of carbon in the periodic table of elements;

• to discuss the structure of the carbon atom;

• to explain the concept of elemental allotropy;

• to present and discuss the properties of diamond, graphite, fullerene and graphene;

• to present and discuss the use of diamond, graphite, fullerenes and graphene;

• to present and discuss the use of allotropic phosphorus and sulfur species;

• to justify the dependence of properties and applications of diamond, graphite, fullerenes and graphene on their internal structure.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• exposing

  • film.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

Realization

1. Willing students on the forum, under the guidance of a teacher, discuss the location of carbon in the periodic table of elements. Then they describe the structure of its atom.

2. The teacher introduces the concept of allotropy. Provides allotropic forms of carbon, oxygen, phosphorus and sulfur.

3. The students consolidate the acquired information, discussing it with their nearest neighbors („tell your neighbor” method).

4. The teacher uses the text of the abstract for individual work or in pairs, according to the following steps: 1) a sketchy review of the text, 2) asking questions, 3) accurate reading, 4) a summary of individual parts of the text, 5) repeating the content or reading the entire text.

5. The teacher instructs students to prepare an observation journal in an abstract (or recommends writing in notebooks). He informs that they will watch the film „Investigation of the electrical and thermal conductivity of graphite”. Before this happens, they are to formulate a research question and hypotheses and note them in the indicated place. After the screening, they set together observations, then conclusions, and write them down as well.

6. At the end of the lesson, the teacher asks students to do an interactive exercise – individual work.

Summary

1. The teacher asks the students to finish the following sentences:

   • Today I learned ...

   • I understood that …

   • It surprised me …

   • I found out ...

   The teacher can use the interactive whiteboard in the abstract or instruct students to work with it

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

2. Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Types of elemental carbon

Some chemical elements, mainly non‑metals, come in various forms that have different physical properties and chemical activity. These forms called allotropes differ in the crystalline structure (e.g. diamond, graphite, fullerenes, graphene) and the number of atoms in the molecule (e.g. ${\text{O}}_{\text{2}}$ – dioxygen, ${\text{O}}_{\text{3}}$ – trioxygen, ozone, ${\text{O}}_{\text{4}}$ – tetraoxygen, red oxygen). This phenomenon is called allotropy, Greek: allos (other) and tropos (type).

Graphite forms the most stable structure of carbon. Its structure is made of flat layers arranged one above the other. Each layer resembles the honeycomb structure. Carbon atoms are arranged in regular hexagons with common sides. Within each layer, the atoms are connected by strong covalent bonds with three neighbouring atoms of this element. However, between the layers there are only weak bonds (van der Waals), therefore graphite crystals are soft and easy to decorticate. Distances between planes are almost 2.5 times greater than the length of bonds between carbon atoms in rings, hence the strength of bonds between layers is small. Therefore, the individual layers of graphite are relatively easy to separate, which we use every time, pressing the pencil to the sheet of paper.

Graphite is a variety of carbon with a black‑greyish colour and metallic gloss. It is very soft (the hardness of the graphite on the Mohs scale is 1), susceptible to abrasion and brittle. It has excellent lubricating properties, is greasy to touch and resistant to high temperatures. It has high mechanical resistance to compression and small resistance to stretching. In addition, graphite and graphite products do not dissolve in water, are characterized by low chemical activity, easy storage and disposal and no negative impact on the environment. Due to these features, it is a modern and ecological material.

This very inconspicuous mineral has various applications in everyday life. Already in the medieval times it was used to write and produce crucibles used in the laboratories of alchemists. Today, we also write with pencils with graphite styli and crucibles and refractory materials (e.g. bricks, carbon blocks, graphite concretes) are still made of it. In addition, this variety is used for the production of: carbon brushes, braking pads in cars, dry lubricants, anti‑corrosive paints, electrodes used for the electrolytic production of metals and electrodes for the production of batteries, moderators (neutron retarding rods) in atomic reactors and construction materials, e.g. graphite composites (these found application for the production of tennis racquets and Formula 1 car components).

For centuries, diamonds delight people with their perfect beauty, rarity and unusual properties. The diamond is made of carbon atoms forming a regular spatial network, shaped like a regular tetrahedron, in which each atom binds with four other carbon atoms. Evenly distributed, short and strong covalent bonds affect the very high hardness of this allotropic type (the Mohs hardness of the diamond is 10).

Pure diamonds usually create colourless, transparent crystals. Because the ions of other elements, e.g. boron, nitrogen, manganese, iron, often occur in their crystalline structure, the vast majority of quarried rocks are coloured. Yellow, red, blue, purple diamonds can be distinguished. There are even black diamonds known, so‑called carbonado. Diamonds are used for cutting glass, due to their greatest hardness among all minerals. It was calculated that a diamond weighing 1 carat – 0.2 g – would be enough to cut a glass panel with a length greater than the distance from Earth to the moon. The fascinating play of lights determines the uniqueness of diamonds among other minerals. After grinding, so‑called brilliant is formed that strongly refract light and also break these down.

Due to its structure, the diamond does not conduct electricity, but it is a very good heat conductor. It is chemically passive. The word diamond comes from the Greek adamas, which means invincible, but it is fragile, and when heated to a temperature of 1100 K it burns.

In 1985, the experiment of scientists Harold Kroto, Richard Smalley and Robert Curl led to the discovery of another variant of allotropic carbon – fullerenes. These are molecules composed of an even number: from 28 to about 1500 carbon atoms, which form a closed block. The most popular fullerene ${\text{C}}_{\text{60}}$ looks like a football ball and is made up of 60 atoms, which form 12 five‑atoms rings and 20 six‑atoms rings. Such geodesic structures resembling molecules ${\text{C}}_{\text{60}}$ were once constructed by R. Buckminster Fuller and the name of this variety originated from the name of this American architect, mathematician and philosopher. This discovery showed a completely new face of carbon – an element that seemed to be perfectly known until now. In addition to fullerenes, nanotubes and nanoballs were also obtained.

An unusual variant of carbon is also graphene, a layer of graphite with a thickness of one atom. Because the graphene layer is extremely thin, it is applied to other materials, which gives them unusual properties. Graphene was obtained in 2004 by Andre Geim and Kostya Novoselov. It is an extremely promising substance. It turned out that the newly discovered form of carbon is the hardest (harder than the diamond) and also the most stretchable known material. It's a great heat conductor – ten times better than silver. As graphite, it is also a very good conductor of electric current, but if it is bonded with hydrogen atoms, it creates a new material, called a graphane, which is a great insulator. Compared with steel, the new material has five to six times lower density, is twice as hard, 13 times more flexible and 100 times more resistant to stretching. Its atomic bonds are so tight that it does not even pass bacteria. Graphene is like a modern philosopher's stone – it also fuels hopes and imaginations, only that we can produce it. Its story is connected with our country, because it is to Polish scientists that we owe the development of industrial technology to receive this extraordinary substance. It is currently the most expensive material, but due to its excellent properties it will certainly replace silicon in the future.

Sulphur forms the most allotropes among the elements – over 30, the most important of which is rhombic sulphur (${\text{S}}_{\text{α}}$) and monoclinic sulphur (${\text{S}}_{\text{β}}$). Both varieties are made of eight‑atom rings (${\text{S}}_{\text{8}}$) differing in the way atoms are arranged in crystals. Rhombic sulphur is stable up to a temperature of 95.6°C. At this temperature, it transforms into monoclinic sulphur. At a temperature of 119.6°C, the monoclinic sulphur melts and becomes a mobile bright yellow liquid -- ${\text{S}}_{\text{λ}}$. When the temperature rises, the sulphur turns brown and thickens – ${\text{S}}_{\text{μ}}$ is formed. Raising the temperature to above 200°C causes the sulphur viscosity to drop, the liquid becomes smooth again without changing the colour. At 445°C, the sulphur boils, giving orange steams made of ${\text{S}}_{\text{8}}$ particles, which during further heating dissociate into smaller and smaller particles (successively into ${\text{S}}_{\text{6}}\text{,}{\text{S}}_{\text{4}}$ and ${\text{S}}_{\text{2}}$). The slow cooling of sulphur causes the reverse order of transformation until the rhombic sulphur is obtained. In contrast, rapid cooling of molten sulphur leads to so‑called plastic sulphur, which has the form of a brown mass. Quickly cooled sulphur vapours condense in the form of a fine yellow powder, called a flower of sulphur.

Phosphorus was discovered in 1669 by the German alchemist Hennig Brandt, who, when searching for a philosopher's stone, roasted concentrated urine with sand without air. During one of these attempts, Brandt received a substance that aroused great interest, mainly because it shone in the dark. In this way, white phosphorus was discovered. Today we know that phosphorus also creates varieties: red, violet and black. These varieties differ not only in some physical properties but also in chemical activity. The white variety is the most active and the chemically passive one is black.

Less well‑known elements occurring in the form of allotropes are: arsenic, antimony, tin, manganese, selenium, uranium, iron.

• The occurrence of the element in types differing in properties is allotropy.

• Graphite, diamond, fullerene and graphene are allotropic types of carbon.

• Graphite has a layered structure. It is soft, conducts electricity and heat well. It is also resistant to high temperatures and its chemical activity is small.

• In the crystalline structure of a diamond, each carbon atom is connected by bonds of the same length to four other atoms of this element. The diamond is very hard, it does not conduct electricity, but it conducts heat well. After polishing it gives multi‑coloured light effects. Its chemical activity is small.

• Fullerene is a molecular type of carbon. These exhibit superconducting and semiconductor properties as well as greater chemical activity in comparison to graphite.

• Graphene is a layer of graphite with a thickness of one atom. It is a very durable and flexible material, preferably conducting an electric current, and after the connection of hydrogen atoms becomes an insulator.

• Allotropic carbon types find many important applications, including in electronics, medicine, industry.